Hemoglobinopathies in India--clinical and laboratory aspects

β-thalassemia is the most common autosomal recessive genetic disorder in India with a mean carrier frequency of 3.3%, and 7500 to 12,000 children with β-thalassemia major are born every year. Subjects with thalassemia trait, also known as carriers, have low mean corpuscular volume, low mean corpuscular hemoglobin, and increased hemoglobin A2 (>4%). Patients with β-thalassemia major have severe anemia and require blood transfusions by 1 year of age, whereas β-thalassemia intermedia patients have mild to moderate anemia and in most cases require no or infrequent blood transfusions. Genotype/phenotype correlation is helpful for the prediction of the phenotype, and deciding treatment options for β-thalassemia patients. Genetic analyses include determining the type of β-globin gene mutation, co-inheritance of α-globin gene deletions/duplications, and Xmn1 polymorphism in γ gene. Success of a β-thalassemia control program depends on prospective carrier screening followed by genetic counseling and prenatal diagnosis.